Displays having optical devices, particularly organic EL displays having organic EL devices have been expected as flat panel displays because of their advantages such as wide view angle, fast response speed, and low power consumption. Each organic EL device that constitutes an organic EL display includes two electrodes (one of which is transparent) and an organic light-emitting medium layer disposed between the electrodes. Current is injected from both of the electrodes so that the organic light-emitting medium layer emits light.
Since optical devices, particularly the organic light-emitting medium layer of the organic EL devices, are degraded by moisture or the like, a method for surface-sealing an organic EL device has been investigated to prevent the moisture or the like from coming in contact with the organic EL device (PTL 1). In other words, an organic EL display has been investigated that includes a pair of substrates and a surface-sealing material disposed between the substrates for surface-sealing the organic EL device. A member for surface-sealing an organic EL device (surface-sealing material) may be in general a cured product of a composition including a thermosetting resin such as epoxy resin curable under conditions which hardly cause deterioration of an organic EL device.
The total thickness of an organic EL device (total thickness of the two electrodes and the organic light-emitting medium layer disposed between the electrodes) is particularly small: about several hundred nanometers thick. As a result, the thickness of an organic EL display is determined substantially by the sum of the thickness of the substrates and the thickness of the surface-sealing material for surface-sealing an organic EL device. An organic EL device is expected for use in a compact and thin display or a backlight member for a cell-phone or the like which is expected to be thinner or more lightweight, and a flexible display or the like having a substrate of flexible plastic.
A problem of a thin substrate for a thin display, however, is that warpage occurs in the display due to, for example, the heat imparted when surface-sealing an optical device, particularly an organic EL device. In order to prevent the warpage of a display, it has been proposed in the art to dispose a warpage prevention layer or an anti-curl layer on the substrate of the display with an adhesive layer interposed in between (refer to PTLs 2 and 3).